It is very well known that microbial activity, ultimately the driver of SOM decomposition, is influenced by climatic parameters.
In particular, the temperature at which microbes are exposed causes an exponential increase of their activity as of any chemical reaction. Lloyd, J., Taylor, J.A., 1994. On the Temperature Dependence of Soil Respiration. Functional Ecology 8, 315.
The water content of soil is a more complicated driver, since it affects the dormancy status of microbes in their micro-enrivonment.